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Message-Id: <20250827-k1-i2c-atomic-v1-6-e59bea02d680@linux.spacemit.com>
Date: Wed, 27 Aug 2025 15:39:13 +0800
From: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
To: Andi Shyti <andi.shyti@...nel.org>, Yixun Lan <dlan@...too.org>,
Alex Elder <elder@...cstar.com>, Troy Mitchell <troymitchell988@...il.com>
Cc: linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev,
Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: [PATCH 6/6] i2c: spacemit: introduce pio for k1
This patch introduces I2C PIO functionality for the Spacemit K1 SoC,
enabling the use of I2C with interrupts disabled.
Signed-off-by: Troy Mitchell <troy.mitchell@...ux.spacemit.com>
---
drivers/i2c/busses/i2c-k1.c | 139 ++++++++++++++++++++++++++++++++++++++------
1 file changed, 120 insertions(+), 19 deletions(-)
diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
index d2c0d20d19ba73baa8b2e9a6acb02b2cc3b7243f..e558fe4cbd5a78b5b53b0c02cbbca818b6495d4a 100644
--- a/drivers/i2c/busses/i2c-k1.c
+++ b/drivers/i2c/busses/i2c-k1.c
@@ -124,6 +124,7 @@ struct spacemit_i2c_dev {
enum spacemit_i2c_state state;
bool read;
+ bool is_pio;
struct completion complete;
u32 status;
};
@@ -228,7 +229,7 @@ static void spacemit_i2c_check_bus_release(struct spacemit_i2c_dev *i2c)
static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
{
- u32 val;
+ u32 val = 0;
/*
* Unmask interrupt bits for all xfer mode:
@@ -236,7 +237,8 @@ static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
* For transaction complete signal, we use master stop
* interrupt, so we don't need to unmask SPACEMIT_CR_TXDONEIE.
*/
- val = SPACEMIT_CR_BEIE | SPACEMIT_CR_ALDIE;
+ if (!i2c->is_pio)
+ val = SPACEMIT_CR_BEIE | SPACEMIT_CR_ALDIE;
/*
* Unmask interrupt bits for interrupt xfer mode:
@@ -246,7 +248,8 @@ static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
* i2c_start function.
* Otherwise, it will cause an erroneous empty interrupt before i2c_start.
*/
- val |= SPACEMIT_CR_DRFIE;
+ if (!i2c->is_pio)
+ val |= SPACEMIT_CR_DRFIE;
if (i2c->clock_freq == SPACEMIT_I2C_MAX_FAST_MODE_FREQ)
val |= SPACEMIT_CR_MODE_FAST;
@@ -258,7 +261,10 @@ static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
val |= SPACEMIT_CR_SCLE;
/* enable master stop detected */
- val |= SPACEMIT_CR_MSDE | SPACEMIT_CR_MSDIE;
+ val |= SPACEMIT_CR_MSDE;
+
+ if (!i2c->is_pio)
+ val |= SPACEMIT_CR_MSDIE;
writel(val, i2c->base + SPACEMIT_ICR);
@@ -295,10 +301,54 @@ static void spacemit_i2c_start(struct spacemit_i2c_dev *i2c)
/* send start pulse */
val = readl(i2c->base + SPACEMIT_ICR);
val &= ~SPACEMIT_CR_STOP;
- val |= SPACEMIT_CR_START | SPACEMIT_CR_TB | SPACEMIT_CR_DTEIE;
+ val |= SPACEMIT_CR_START | SPACEMIT_CR_TB;
+
+ if (!i2c->is_pio)
+ val |= SPACEMIT_CR_DTEIE;
+
writel(val, i2c->base + SPACEMIT_ICR);
}
+static irqreturn_t spacemit_i2c_irq_handler(int irq, void *devid);
+static int spacemit_i2c_wait_pio_xfer(struct spacemit_i2c_dev *i2c)
+{
+ u32 msec = jiffies_to_msecs(i2c->adapt.timeout);
+ ktime_t timeout = ktime_add_ms(ktime_get(), msec);
+ int ret;
+
+ while (i2c->unprocessed && ktime_compare(ktime_get(), timeout) < 0) {
+ udelay(10);
+ i2c->status = readl(i2c->base + SPACEMIT_ISR);
+
+ spacemit_i2c_clear_int_status(i2c, i2c->status);
+
+ if (!(i2c->status & SPACEMIT_SR_IRF) && !(i2c->status & SPACEMIT_SR_ITE))
+ continue;
+
+ spacemit_i2c_irq_handler(0, i2c);
+
+ i2c->status = readl(i2c->base + SPACEMIT_ISR);
+
+ /*
+ * This is the last byte to write of the current message.
+ * If we do not wait here, control will proceed directly to start(),
+ * which would overwrite the current data.
+ */
+ if (!i2c->read && !i2c->unprocessed) {
+ ret = readl_poll_timeout(i2c->base + SPACEMIT_ISR,
+ i2c->status, i2c->status & SPACEMIT_SR_ITE,
+ 30, 1000);
+ if (ret)
+ return 0;
+ }
+ }
+
+ if (i2c->unprocessed)
+ return 0;
+
+ return 1;
+}
+
static int spacemit_i2c_xfer_msg(struct spacemit_i2c_dev *i2c)
{
unsigned long time_left;
@@ -312,10 +362,27 @@ static int spacemit_i2c_xfer_msg(struct spacemit_i2c_dev *i2c)
reinit_completion(&i2c->complete);
- spacemit_i2c_start(i2c);
+ if (i2c->is_pio) {
+ disable_irq(i2c->irq);
+
+ /*
+ * The K1 I2C controller has a quirk:
+ * when doing PIO transfers, the status register must be cleared
+ * of all other bits before issuing a START.
+ * Failing to do so will prevent the transfer from working properly.
+ */
+ spacemit_i2c_clear_int_status(i2c, SPACEMIT_I2C_INT_STATUS_MASK);
+
+ spacemit_i2c_start(i2c);
+ time_left = spacemit_i2c_wait_pio_xfer(i2c);
+
+ enable_irq(i2c->irq);
+ } else {
+ spacemit_i2c_start(i2c);
+ time_left = wait_for_completion_timeout(&i2c->complete,
+ i2c->adapt.timeout);
+ }
- time_left = wait_for_completion_timeout(&i2c->complete,
- i2c->adapt.timeout);
if (!time_left) {
dev_err(i2c->dev, "msg completion timeout\n");
spacemit_i2c_conditionally_reset_bus(i2c);
@@ -343,6 +410,9 @@ static bool spacemit_i2c_is_last_msg(struct spacemit_i2c_dev *i2c)
static void spacemit_i2c_handle_write(struct spacemit_i2c_dev *i2c)
{
+ if (!(i2c->status & SPACEMIT_SR_ITE))
+ return;
+
/* if transfer completes, SPACEMIT_ISR will handle it */
if (i2c->status & SPACEMIT_SR_MSD)
return;
@@ -355,14 +425,20 @@ static void spacemit_i2c_handle_write(struct spacemit_i2c_dev *i2c)
/* SPACEMIT_STATE_IDLE avoids trigger next byte */
i2c->state = SPACEMIT_STATE_IDLE;
- complete(&i2c->complete);
+
+ if (!i2c->is_pio)
+ complete(&i2c->complete);
}
static void spacemit_i2c_handle_read(struct spacemit_i2c_dev *i2c)
{
+ if (!(i2c->status & SPACEMIT_SR_IRF))
+ return;
+
if (i2c->unprocessed) {
*i2c->msg_buf++ = readl(i2c->base + SPACEMIT_IDBR);
i2c->unprocessed--;
+ return;
}
/* if transfer completes, SPACEMIT_ISR will handle it */
@@ -375,7 +451,9 @@ static void spacemit_i2c_handle_read(struct spacemit_i2c_dev *i2c)
/* SPACEMIT_STATE_IDLE avoids trigger next byte */
i2c->state = SPACEMIT_STATE_IDLE;
- complete(&i2c->complete);
+
+ if (!i2c->is_pio)
+ complete(&i2c->complete);
}
static void spacemit_i2c_handle_start(struct spacemit_i2c_dev *i2c)
@@ -410,7 +488,9 @@ static void spacemit_i2c_err_check(struct spacemit_i2c_dev *i2c)
spacemit_i2c_clear_int_status(i2c, SPACEMIT_I2C_INT_STATUS_MASK);
i2c->state = SPACEMIT_STATE_IDLE;
- complete(&i2c->complete);
+
+ if (!i2c->is_pio)
+ complete(&i2c->complete);
}
static irqreturn_t spacemit_i2c_irq_handler(int irq, void *devid)
@@ -418,13 +498,20 @@ static irqreturn_t spacemit_i2c_irq_handler(int irq, void *devid)
struct spacemit_i2c_dev *i2c = devid;
u32 status, val;
- status = readl(i2c->base + SPACEMIT_ISR);
- if (!status)
- return IRQ_HANDLED;
+ /*
+ * In PIO mode, do not read status again.
+ * It has already been read in wait_pio_xfer(),
+ * and reading it clears some bits.
+ */
+ if (!i2c->is_pio) {
+ status = readl(i2c->base + SPACEMIT_ISR);
+ if (!status)
+ return IRQ_HANDLED;
- i2c->status = status;
+ i2c->status = status;
- spacemit_i2c_clear_int_status(i2c, status);
+ spacemit_i2c_clear_int_status(i2c, status);
+ }
if (i2c->status & SPACEMIT_SR_ERR)
goto err_out;
@@ -483,11 +570,14 @@ static void spacemit_i2c_calc_timeout(struct spacemit_i2c_dev *i2c)
i2c->adapt.timeout = usecs_to_jiffies(timeout + USEC_PER_SEC / 10) / i2c->msg_num;
}
-static int spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, int num)
+static inline int
+spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, int num, bool is_pio)
{
struct spacemit_i2c_dev *i2c = i2c_get_adapdata(adapt);
int ret;
+ i2c->is_pio = is_pio;
+
i2c->msgs = msgs;
i2c->msg_num = num;
@@ -510,18 +600,29 @@ static int spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, in
if (ret == -ETIMEDOUT || ret == -EAGAIN)
dev_err(i2c->dev, "i2c transfer failed, ret %d err 0x%lx\n",
- ret, i2c->status & SPACEMIT_SR_ERR);
+ ret, i2c->status & SPACEMIT_SR_ERR);
return ret < 0 ? ret : num;
}
+static int spacemit_i2c_int_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, int num)
+{
+ return spacemit_i2c_xfer(adapt, msgs, num, false);
+}
+
+static int spacemit_i2c_pio_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, int num)
+{
+ return spacemit_i2c_xfer(adapt, msgs, num, true);
+}
+
static u32 spacemit_i2c_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
}
static const struct i2c_algorithm spacemit_i2c_algo = {
- .xfer = spacemit_i2c_xfer,
+ .xfer = spacemit_i2c_int_xfer,
+ .xfer_atomic = spacemit_i2c_pio_xfer,
.functionality = spacemit_i2c_func,
};
--
2.50.1
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